The present invention relates to a control method of stop waiting operation in a collective packing machine where articles packed in specified size by a main packing machine (front packing machine) are packed in collective packing (using a packing paper of specified size) by an auxiliary packing machine (rear packing machine).
In order to control the operation of such a collective packing machine in the prior art, a control method of stop waiting operation has been adopted.
A control method of stop waiting operation is characterized in that packed articles fed continuously at regular intervals from a main packing machine in continuous operation are received, in an auxiliary packing machine; the auxiliary packing machine in stop waiting state is started for operation when packed articles in the required number are received, and after finishing one cycle operation of auxiliary packing to perform collective packing of the packed articles the auxiliary packing machine is in stop waiting state at a predetermined definite position.
In such operation control method, however, a condition must be satisfied that one cycle time of the auxiliary packing shall be less than one lot cycle of the main continuous packing of articles in the prescribed number and lines in the main packing machine.
For example, in order to perform collective packing of packed articles of one lot being two stages by five lines, the auxiliary packing machine must finish the collective packing of articles in two stages by five lines before the main packing machine finishes to manufacture packed articles in two stages by five lines being ten pieces.
If one cycle time of the auxiliary packing is delayed in comparison to one lot cycle of the main packing, normal flow of packed articles at an article delivery position becomes impossible and operation of the main packing machine must be stopped. In order to satisfy the above-mentioned condition and expect a stable operation, the waiting time before starting one cycle of the auxiliary packing must be as long as possible, and since one cycle time of the auxiliary packing is made less than one lot cycle of the main packing the operation speed of the auxiliary packing machine must be rapid.
This tendency becomes more significant as high speed operation advances, and therefore it adversely affects the auxiliary packing machine in its operation and mechanism.
The driving method of the auxiliary packing machine in the prior art is such that a motor of the auxiliary packing machine is in a continuous operation state and the clutch/brake mechanism, for example, is connected or thereto disconnected whereby drive transmission to an acting member is controlled.
In the drive transmission method using such clutch/brake mechanism, however, a time interval between the clutch connection starting and the connection finishing (slip between input and output shafts being zero and the revolution speed being equal) is inevitably required. The connection finishing time becomes longer as high speed operation advances. Consequently, ratio of the connection finishing time in one cycle time of the auxiliary packing becomes large, and in order to satisfy the above-mentioned condition the speed ratio between the main packing machine and the auxiliary packing machine must be further increased.
In phase relation between the auxiliary packing machine and the main packing machine, since the auxiliary packing machine must be operated in synchronization as soon as possible after the operation starting, the operation speed of the auxiliary packing machine must be further increased so as to recover the phase delay of the auxiliary packing machine. Since times for stopping and starting per minute increase as the high speed operation advances, the operation condition of the auxiliary packing machine becomes further disadvantageous.
In some collective packing machines of the prior art, the auxiliary packing machine can be operated continuously. In order to eliminate disadvantages caused by intermittent operation of stopping or starting a reservoir of large capacity is installed in an intermediate portion of a delivery path between the main packing machine and the auxiliary packing machine. The operation speed of the main packing machine or the auxiliary packing machine is variable in correspondence to the pool amount in the reservoir which is controlled constantly so as to enable the continuous operation of the auxiliary packing machine within the desired extent.
In this type of packing machine, existence of the reservoir requires a large installation area and increases the overall cost of the facilities thereby various disadvantages are involved in its practical use. In view of the disadvantages of such packing machine, a control method of stop waiting operation as described previously is preferred.